Sunday, July 19, 2015
Fixing Climate: What Past Climate Changes Reveal About the Current Threat - and How to Counter It
Book Review: Fixing Climate: What Past Climate Changes Reveal About the Current Threat – and How to Counter It – by Wallace S. Broecker and Robert Kunzig (Hill & Wang, 2008)
This was a great book, very readable. Wally Broecker is a legendary and very influential geoscientist eminently qualified to work on the world’s ocean and climate issues. He discovered and elaborated on the oceanic circulation system known as the “conveyor belt.” This unique book also reads as a quasi-biography of Broecker’s life and knowledge. Broecker had read and liked Kunzig’s book about oceanography so he chose the popular science writer as a co-author to tell his story of climate, which he has been studying since the mid-1950’s. One of Broecker’s ideas is that climate change is often not gradual but abrupt in situations where the oceanic circulation is jammed and possibly in other situations as well. Such situations have come to be called “tipping points.” Yet the authors note that climate change may not outweigh human misery as a problem of humanity and they contend that climate can be fixed. They do, however, acknowledge that the predictions of the IPCC of 1.8-4 deg Celsius of temperature rise by 2100 could actually be conservative. They also acknowledge the role of fossil fuels in taking many people out of miserable conditions. They note that we solved the problems of human waste – cesspools that led to deadly outbreaks of typhoid fever and cholera in the 1800’s and so too may we solve the problems of fossil fuel emissions waste. Broeker and colleagues seem to think that the analogy is proper and that mitigation techniques like various types of carbon sequestration and geoengineering are feasible. The latter part of the book goes into the fixing climate part.
When Broecker was still a grad student he had a turning point in his life one summer when he was invited by archaeological curator and paleontologist Phil Orr to help radiocarbon date terraces at Pyramid Lake in Nevada. Broecker was adept at this new and exciting technique and Orr got many dates for free. Broecker grew up in Chicago at the bottom of an Ice Age lake, though he didn’t know it at the time. Here the book goes through young Broecker’s biography, tracing his interest in science. He was known for his practical joking and that could get elaborate. He was offered a summer job in a lab at Lamont-Doherty and this crystallized his interest in science. This is where he learned radiocarbon dating and got to be expert at it.
Along with Broecker’s life events there is mixed in much history of glaciology, oceanography, and climate science. The story of Ice Ages and the unraveling of planetary and celestial effects on climate by Milankovic is recounted. The Milankovic cycles involve the effects of planetary orbits, especially Jupiter, the eccentricity, or elliptical nature, of the earth’s orbit around the sun, and the effect of precession, or the earth’s wobbling on its axis, caused by the gravitational pull on the equator by sun and moon. Each of these effects combines to alter the solar radiation received by different parts of the earth, both land and ocean, at different times. These effects were discovered in the 19th century but first abled to be quantified in detail by Milankovic in the early 20th century. These calculations are now routinely input into climate models. In the 1920’s Wladimir Koppen (who with his nephew Alfred Wegener came up with the theory of continental drift) contacted Milankovic. Koppen considered that it was the retention of summer ice that was the key to the growth of ice sheets, though some still dispute this – favoring instead warm tropical winters that evaporate enough water to cause more snowfall near the poles. Milankovic sent Koppel his data and there was found a very good match between the planetary cycles and ice ages. However, there were problems with the correlation and by the time Milankovic died in 1958, his theory had fallen out of favor. He never got to know about its resurgence, later. However, after the advent of radiocarbon dating, the ice ages could be more accurately dated. Both Milankovic’s and Wegener’s theories would emerge in more detailed forms – Wegener’s in the new theory of Plate Tectonics and Milankovic’s in the finding of more and better proofs of correlations between orbital cycles and ice ages.
Even though Broecker’s specialty, radiocarbon dating, was used to refute the accuracy of Milankovic cycles, it was limited to about 35,000 yrs since samples older than that did not have enough carbon remaining to get an accurate date. Since the Milankovic cycles were on the order of 20,000 or 40,000 or 100,000 yrs, the use of radiocarbon dating would be quite limited and not really useful to the task. One of Broecker’s grad students discovered that Uranium-thorium dating could be used to date corals as far back as 200,000 years. The coral reef terraces ringing the island of Barbados accurately recorded sea level changes over hundreds of thousands of years. The biggest changes in sea level correspond to the interglacials and the ice ages. Broecker’s work with corals in the late 1960’s served to both prove and update/recalculate some of Milankovic’s conclusions:
“… there were now four well-dated rises in sea level that corresponded to peaks in Milankovic’s sunlight curve, as modified by Broecker.”
By the early 1970’s the use of oxygen isotopes (O16 and O18) were used as a proxy for climate in sea floor sediment cores which preserved a more continuous record of climate than coral reef terraces. These also were found to match fairly well with predicted Milankovic orbital cycles. However, Milankovic cycles were not predicted to affect both the northern and southern hemispheres of the earth simultaneously, but in some cases it was shown that climate events did affect the whole earth. A feedback from the ocean and/or atmosphere was likely involved – quite possibly carbon dioxide. A few decades later it would be discovered from ice cores in both Greenland and Antarctica, that CO2 and climate have changed together for the last 800,000 years. During the 1970’s there was concern about global cooling and the possibility of another ice age as a cooling trend from the 1940’s into the 1970’s was apparent. Broecker, however, was more concerned about global warming and the effect of CO2 as a greenhouse gas in the current interglacial which he thinks could last as much as another 10,000 or even 20,000 years.
The authors give a history of CO2 measurement, the greenhouse effect, and early climate science. The ideas of Arrhenius, Fourier, Tyndall, Hogbom, Callendar, Revelle, Suess, and finally Charles David Keeling, are recounted. Keeling became adept at measuring CO2, in water and in air. He figured out ways CO2 was used in water and air and how concentrations of the gas differed according to different circumstances. Keeling measured air concentrations of CO2 and found that it was consistent globally, at that time, the late 1950’s, it was 315-320 ppm. Keeling kept up continuous measurements of CO2 at Mauna Loa in Hawaii and this became the famous “Keeling curve,” which showed a 20% increase of CO2 from 1958 to 2008 in a regular pattern. Statistics on fossil fuel use also showed a regular increase and the likelihood that the rise in CO2 was due to the rise of fossil fuel use is undeniable.
In 1957 Broecker designed a sampling regimen of CO2 from seawater with samples taken a mile below the surface. One reason to do this was to have enough carbon in the seawater samples to radiocarbon date them in order to determine how long it took the water to get to those depths, with the goal of understanding ocean circulation. Broecker and others found that radiocarbon (Carbon -14) had a spike due to nuclear tests by Russia and the US between 1952 and 1963 so that the spike could be used to track the flow of carbon during that time period. Ralph Keeling, David Keeling’s son, started measuring atmospheric oxygen in the late 1980’s. His idea was that O2 levels should rise slower than they would otherwise due to fossil fuel releases of CO2 and the amount of CO2 absorbed by the ocean could be accurately predicted by measuring O2 levels. Ralph devised an ingenious method of O2 measurement using an interferometer, measuring O2 vs. unchanging nitrogen at accuracies within 1 part per million. His measurements show that O2 is falling as CO2 rises. By comparing the differences in O2 fall vs. CO2 rise it can be predicted how much CO2 is taken up by the land and ocean. His modeling suggests that over the last 25 years or so about 35% of fossil fuel CO2 went into the ocean and 15% went into the land. That suggests that 50% went into the atmosphere. The capacity of the ocean to take in CO2 is decreasing and by the second half of this century the ocean may be absorbing less CO2 than now. Increased CO2 and warmer temps in the arctic have led to forests creeping northward. More CO2 can mean faster seasonal growth. This will slightly increase the uptake of carbon by the land.
Climate models predicted the ocean temperature in the Eocene (55 million years ago) but cores drilled into the sea floor of the Arctic Ocean revealed that the temperatures were 18 deg F higher than the highest model prediction. An unpredicted feedback was needed to explain the higher temps. It was likely CO2 spewed copiously from volcanoes. From this greenhouse maximum it took about 10 million years for the next icehouse to form. By 2 million years ago the greenhouse-icehouse cycles triggered by the Milankovic orbital cycles began, although icehouse conditions are noted/suggetsed as far back as the Ordovician, over 400 million years ago. Due to our fossil fuel combustion we have altered atmospheric and oceanic CO2 concentrations much faster than nature has. However, there are indications that some past natural climate variations occurred quite quickly, in a decade or less.
Oxygen isotope variations in air bubbles trapped in the summer snows of ice cores showed some regular climatic variations on scales that might correlate with sun cycles. Broecker thought in 1975 that a cooling due to a solar low output was masking global warming and would accelerate it when it returned to higher output. Temperatures did turn out to follow such a pattern. By 1982 it was possible to extract and measure the level of CO2 in the bubbles. About this time Broecker was getting the idea that changes in the ocean’s thermohaline circulation (heat-salinity circulation), the conveyor belt, could change climate. He discovered that with both radiocarbon dating and measuring amounts of oxygen and phosphates in seawater he could calculate how fast the deeper ocean currents moved. The idea is that colder denser waters sink and spreads out, eventually getting heated by solar radiation and then begins rising again. The dominant place where this occurs is in the North Atlantic where surface water from the tropics, made more salty by evaporation, sinks. Continental winds, trade winds, and precipitation fuel this flow of surface waters. The newly deep heat and salt is transferred back out of the Atlantic southward then eastward into the Pacific, then the cycle begins again. The whole process takes several centuries. Broecker described all the details. He noted the Younger Dryas, a period from about 12,900 years ago when temps had heated up to those similar to now after the Last Glacial Maximum (LGM) to about 11,400 years ago. During those 1500 years the ice age returned. His idea was that Lake Agassiz, a lake larger than all the Great Lakes combined and was formed due to the initial melting of glaciers, had burst a moraine dam thus entering the Atlantic all at once near enough to the place in the North Atlantic (just south of Iceland) where the sinking of the surface waters took place. This had the effect of making the water fresher, thus shutting off the conveyor belt, which resulted in a return of ice age conditions. However, as Broecker discovered, there is much more to what triggered the Younger Dryas and other cyclical events such as the Daansgard-Oeschger events (abrupt warming events) and Heinrich events (cyclical layers of debris dropped to the ocean bottom by melting ice bergs).
Next, the story is told of Penn State glaciologist Richard Alley and the Greenland Ice Core (GISP2). By examining isotope ratios and actual temperature measurements in the borehole it was determined that some of the temperature changes were extreme. Differences between avg. summer temps and avg. winter temps were much more than today during certain times, which suggested to Broecker that the Atlantic was frozen during those times. The shutting down of the oceanic conveyor belt may have actually triggered the melting of glaciers along with Milankovic solar increases. Beginning around 17,500 years ago the ice from the Last Glacial Maximum began to melt and the CO2 locked under it began to be re-released to the atmosphere. What actually happened is difficult to predict but it was likely due to a combination of cycle resonances and catastrophic events related to icebergs and ocean circulation. Predicting and modeling climate events that took place tens of thousands of years ago is a bit difficult but Broecker’s switching on and off the ocean conveyor belt system resulting in a climatic hot state and a climatic cold state (greenhouse vs. icehouse), explains a lot about how the changes could be further triggered after initial triggering by Milankovic and other cycle coincidences. Scenarios for these climate events such as the Younger Dryas have been extensively modeled. It is uncertain how the freshwater got to the Arctic to shut down the conveyor system by making the water less salty and less dense. It could have been from fast melting ice bergs or it could have been from the draining of Lake Agassiz. However, there is evidence from sediment cores that the conveyor did indeed shut down during the Younger Dryas.
Broecker is somewhat of a dinosaur – doesn’t like email, barely ever uses a computer, writes things out by hand, etc. He is also realistic and humble in the sense that he can relinquish an idea if the evidence is against him. When trying to find evidence for the draining of Lake Agassiz, he has failed so far. Some of his other ideas did not pan out as well and he notes that science is like that, sometimes you miss the picture but then you need to go back and redraw it.
Melting glaciers and the forming of new glacial lakes is clear evidence for global warming. This has been happening since the 1950’s in New Zealand where new lakes began to form in the mid-60’s. Ocean surface temps have risen faster there than the global average. Prevailing winds have changed direction there due to higher ocean temps. However, it is also true that the current glacial retreat began in the 19th century long before industrial CO2 emissions climbed. The authors point out importantly that the two main issues to be worked out in regards to global warming are: 1) How bad is it? and; 2) What should be done about it? Another very good indicator of global warming is the shifting poleward of plant and animal species ranges.
The 2004 movie The Day After Tomorrow depicted a catastrophe caused by a shutdown of the oceanic conveyor belt, one that was not realistic. Broecker does not think that is likely to happen at current projections of warming. However, there is evidence that North Atlantic ocean water has gotten slightly more fresh and that currents have slowed down. He thinks this will simply slow down the conveyor.
Devastating sea level rise is a major concern of climate change studies. Although climate change skeptics often complain that the IPCC is alarmist, there are many, including many scientists, who think it is too conservative. We still do not know how bad it is or will be. This is one reason the IPCC gives all their modeling results and conclusions in a range of scenarios.
During the last interglacial the temps were warmer at the poles due to the Milankovic effects of increased solar radiation at the polar latitudes. Greenland’s ice melted fully in summer and sea level was about 3.5 meters higher. In some places sea level has risen 120 meters (400 ft) since the LGM (Last Glacial Maximum). The IPCC report in 2001 predicted that glacial melting will be predictable but some glaciologists disagree. It depends on whether scientists have the mechanisms of ice sheet disintegration and collapse correct. One negative feedback of global warming is that the warmer air carries more moisture, particularly more moisture is carried over interior Greenland and Antarctica where it falls as snow, more snow than in a cooler world. In some places it is clear that the rate of melting is far exceeding the rate added by increased snow. Another fear is a collapse of the West Antarctica ice sheet. This is of course more likely in a warming world.
Another possible effect of global warming are mega-droughts in certain areas. A warmer climate effects weather patterns which sequester moisture in certain areas and deprive other areas of it. This is not easy to predict on a local or weather scale but overall trends and effects can be modeled. Comparisons to past mega-droughts caused by climate change are factored into those models. Global warming changes weather in ways that are unpredictable locally and temporally but trends can be modeled based on past climate changes. The usual warning is that weather will in general get more intense as storms have more moisture available and wind patterns change, depriving rain to some areas. The same argument, unpredictability of weather effects, is used to discourage the use of geoengineering to mitigate climate change. Another effect of a warming world is that more precipitation will fall as rain and less as snow in the mid-latitudes and there will be less snow melt to feed freshwater reservoirs and aquifers. There is evidence that this is already happening in the American Southwest and especially in California where the Sierra mountains snow melt has been sparse the last several years. Glaciers and snow pack provide the main source of water to one sixth of the world’s population. Long mega-droughts are documented in California, several of them, with the severest in the 1100’s and one ending in 1350. The current drought, though so far less severe than the mega-droughts, is still in progress.
Some researchers think a warmer climate favors La Nina conditions that also contribute to drought in the American Southwest. Broecker thinks the Medieval Warm Period and the Little Ice Age were part of the same cycle triggered by solar variations. Those changes allowed the Vikings to colonize Greenland and then helped force them to abandon it. They may have also led to the breakup due to drought of the Mayan and Anasazi civilizations. The authors note that the Medieval Warm Period and the Little Ice Age suggest that the climate is very sensitive to small inputs. Most climate models predict a dryer American southwest – the greater the global warming, the drier the region. Australia had been having severe drought for several years due to El Nino conditions but that one finally ended.
Despite some warnings to the contrary, it appears we have enough fossil fuels to last at least a few centuries. Currently, developing countries like China, India, South Korea, Brazil, and others are increasing CO2 emissions while the U.S. has stabilized our massive amount of emissions. Of course, per capita emissions are still higher in the U.S. and Europe. China has been the biggest emitter since 2006. High oil and gas prices lead to more coal usage unless coal usage is curbed via environmental regulations. Coal, along with wood, is the most polluting and the highest CO2 emitter of the fossil fuels (and biomass). James Hansen first put the CO2 threshold at 450 ppm to threaten the ice sheets but now considers a return to 350 ppm as being better. Realistically about 560 ppm is where we may peak on CO2. Much is dependent on adoption of renewable energy (solar, wind, hydro, not biomass) and nuclear and these sources do not seem to be up to the task on as large of a scale needed. Therefore the authors advocate careful geoengineering. They think some methods of geoengineering can work safely and effectively to reduce CO2 in the atmosphere. Princeton University researchers have proposed ways to reduce emissions through efficiency, technology, and energy sourcing: increase vehicle fuel mileage from 30 to 60mph, cut vehicle travel, build more nuclear power plants, and add more renewables. One interesting argument in line with geoengineering is the observation that mass implementation of wind turbines would likely slow down wind across the planet. This would also slow down the transfer of heat and moisture across the planet, effectively altering climate. This could affect climate in different areas. This has yet to be modeled effectively to my knowledge. Thus, there are unknowns with such implementation similar to those with geoengineering. Broecker taught a course in the early 1980’s from his book, How to Build a Habitable Planet, which considered the CO2 emissions problem. Even now he still thinks there is not a feasible way to keep emissions from peaking at around 560 ppm. However, now he does think it is possible to mitigate some of the climate effects through careful geoengineering projects.
Broecker met Klaus Lackner in 1998 or 1999 when Broecker spoke at a conference about the CO2 problem and Lackner, a German physicist, spoke about how to solve it by accelerating the process of geochemical weathering – where CO2 reacts with magnesium and calcium-rich minerals to make magnesium or calcium carbonates. Broecker and Lackner met again at Biosphere 2, a billionaire’s experiment that was having problems with low oxygen levels. Broecker immediately recognized the problem – bacteria in the soil were consuming oxygen and respiring CO2 and the plants could not photosynthesize fast enough to take up the excess CO2. The project had predicted excess CO2 in winter and installed a scrubber to remove it with sodium hydroxide. The base of the concrete walls were also found to be removing some by precipitating a calcium carbonate crust. Lackner had worked on many scientific projects but his latest idea was removing CO2 from the air on a large scale. CO2 makes up from one tenth to one sixth of flue gases but is only at a concentration of about one-three thousandth in ambient air – this is equivalent to being three hundred times more dilute. Lackner has calculated that it is, however, doable to extract CO2 from ambient air, even though groups like the IPCC dismiss it as impractical and instead consider it more feasible to extract CO2 from power plant flue gases. It should be noted here that it is easier and cheaper to extract CO2 from natural gas power plants than it is from coal plants. However, there is some new technology being developed currently that may make it easier to extract from coal by trapping it earlier in the combustion process. Broecker agreed that Lackner’s ideas had merit and he was recruited from Los Alamos to Columbia. Then they recruited a layed off engineer from Biosphere 2 (which was bought by Columbia then abandoned due to cost) named Allen Wright. Wright had previously worked as a pilot for a submersible on scientific missions, where he had a reputation of being a problem solver. Wright would become the builder of the prototypes. Initial funding would come from billionaire entrepreneur Gary Comer, who witnessed the opening of the Northwest Passage through his many yacht travels in the Arctic and North Atlantic. They referred to the money as “adventure capital.” Wright’s brother would also help him build the device, thus the Wright brothers would build it! Broecker considered that a good omen. The challenge was to invent a way to extract sufficient CO2 from the air without expending too much energy so that there is an economic upside and assurance of sufficient emissions benefits. The company formed is called Global Research Technologies. After building and testing several models they announced that they had one ready, a pre-prototype Allen Wright called it, in 2007 but with no details yet made public about how it works. The plan for them to be deployed would be similar to those of windfarms. This makes me consider a life cycle or project energy balance to determine how much emissions would actually be reduced overall. I also wonder whether such devices could be attached to existing poles for wind turbines or included in the design with new ones. The air scrubbers offer the advantage of taking CO2 directly out of the air. About a third of anthropogenic CO2 and 40% of it in the U.S. is produced by mobile sources. The air scrubber can access all sources while the point sources at power plants can be captured there. This is beginning to happen now and likely will continue with small to moderate increases in electricity prices likely because of it.
After the CO2 is captured it needs to be disposed of, stored, sequestered. This is a daunting problem as well. Underground reservoirs have been identified and modeled. Projects have been technologically successful with actual conditions being close to model predictions in CCS projects. Economic success is probably dependent on a taxed carbon situation. In some gas fields CO2 has been stripped and sequestered. This has been done since 1996 in Statoil’s Sleipner Field in the North Sea where the gas in 10% CO2 and in order to avoid a local carbon tax situation the CO2 is pumped back underground. Millions of tons of CO2 is pumped into the ground in the U.S. for enhanced oil recovery and that amount continues to rise. Of course, due to extraction of more oil, these enhanced oil recovery projects are only a short-term help to the carbon problem. Deep saline aquifers offer the best reservoirs to sequester CO2 and the process can go faster as a geochemical reaction that yields stable carbonate rocks when the CO2 is injected into basalt lava rock, although I don’t think this has been done on any large scale project. In 2006 Broecker went to Iceland, an island surrounded by basalt. He was invited by the president. Iceland, a country of only 300,000 population, was once fueled by British coal but has since developed its significant geothermal and hydroelectric resources. However, some of the geothermal wells drilled by Reykjavik Energy have yielded CO2 and hydrogen sulfide. They want to re-sequester those gases in the basalt. This project was slated to begin in 2008. It would interesting to check on it as well as the progress of Global Technology Resources air CO2 capturing technology. Most agree that subsurface geological CO2 sequestration is limited by economics and amount of available reservoir. Mineral sequestration – by reaction with calcium and magnesium-rich rocks has the problem of exposing (by mining techniques) rock and disposing a greater volume of rock. Some think the new material could be made into cement building materials. Mineral sequestration is probably a few decades away, in any case. Some advantages are that the sequestration of the CO2 is more or less permanent. Another possible advantage is that there are way more than enough ultramafic rocks distributed around the earth to dispose of all the CO2 we produce with fossil fuels.
Russian climatologist Mikhail Budyko first proposed injecting sulfur dioxide into the air to mitigate global warming. Broecker and physicist John Nuckolls redid Budyko’s calculations and determined the cost of acquiring sulfur and delivering 35 million tons of the product via Boing 747s. They came up with about 60 billion bucks then in 1984. This is a per year cost as it does not stay long in the atmosphere. Of course, there are several potential problems with this sort of geoengineering: changing weather patterns, acid rain, and dangerous particulate matter. Injecting it directly into the stratosphere would be better and reduce or eliminate those problems to varying degrees. The use of balloons has been proposed. Broecker and his colleagues often compare the CO2 disposal problem to the sewage disposal problem in the nineteenth century. They see CO2 capture in air, not as geoengineering like injecting SO2, but simply as cleaning up after ourselves, similar to sewage treatment. That is certainly a different way to look at it. Economic modeling shows that reasonable carbon taxes would make CO2 sequestration economically feasible and air capture could become more feasible as well. What they suggest is the development of a new carbon disposal industry. Developing countries like China and India need pollution control equipment to slow their emissions of both greenhouse gases and dangerous pollutants. The U.S. and other long-term emitters could take the lead in carbon disposal to mitigate emissions and sell the initial pollution control equipment to those developing countries who need it now. If humans can eventually develop the ability to control the amount of greenhouse gases we emit then we could potentially control climate, perhaps averting future ice ages. Of course, the ethics and logistics of such control would be a matter for much debate.